Process for treating metals



Nov. 7, 1933. J. o. BETTERTON El AL 1,934,430

PROCESS FOR TREATING METALS Original Filed Nov. 11', 1931 Patented Nov. 7,, 1%33 TES this IEEQCESS FGR TREATHNG METALS Griginal application November lll, 1931, Serial No.

574,328.. litividcrl and this application April 7,. 1933a Scriai Nib. 66%,854:

16 Claims This invention relates to a; process for treating metals, and more particularly to a process for the removal of zinc from lead, such as zinc bearing lead, resulting from the desilverisation practice in lead refining. The invention provides for the removal of the zinc as a slag and for the processing of the slag for the production of a valuable high zinc end product substantially free from lead.

The process is carried out by removing a portion of the zinc from the lead bath by means of chlorine gas and removing a further portion by means of an oxidizing agent, such as air, steam or water, and combining the portionsso removed to produce a zinc oxychloride slag having a corn trollable amount of chlorine present therein and by deleading the oxychloride slag to produce a zinc product which can be readily processed for the production of commercial zinc oxide. The process is so carried out that the various by products are utilized in a cyclic manner and the final products are removed from thc'lead in a commercially usable form.

The invention further consists in the new and novel features of operation and the new i and original arrangements and combinations of steps in the process hereinafter described and more particularly set forth in the claims.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and ad vantages, and the manner in which it may be carried out, may be better understood by refer= ring to the following description taken in con nection with the accompanying drawing forming a part thereof, in which Fig. l is a broken plan view of one form of apparatus by which the present process may be carried out; J

Fig. 2 is a section taken on. the line 2-2 of Fig 1 showing the dezincing chambers; and

Fig. 3 is a broken elevation of the stirring device.

Like reference characters denote like parts in r the several figures of the drawing In the following description and in the claims, various details will be identified by specific names for convenience but they are intended to be as generic in their application as the art will permit.

Referring to the drawing more in detail, the ap-= paratus is shown as comprising a kettle 10 which is adapted to contain a bath-11 of molten lead,

The kettle 10 is provided with a rim' 12..which rests upon a. supporting member 13, such as a floor, by which the kettle is held in operating position with respect to suitable heating devices not shown. Resting upon the rim of kettle 10 is a frame- 'worlr l4: comprising'longitudinal members which support a pair of chambers 15 and 16, pump 17, so gear box 18 and driving motor 19. Pump 17 is suspended belowframework 1 as by struts 2d and is adapted to be immersed in bath 11 whereby material from said bath is. discharged through pipe 21 into chambers 15 and 1s. Said pipe 21 is es provided with a forked section 22, the two branches 23-434 of which communicate through the topof chambers 15 and 16 respectively and are adapted to apply molten metal thereto. Valve 25 may be included in pipe 21 in a position '20 near pump 17 so that the flow of metal can be prevented when the pump is first placed in position and the operation is begun. This permits the pump to be brought up to full operating speed before any metal is discharged into chambers 15 7s and. 16. Valves ZSa-nd 27 are located in branches 232 l respectively of forked member 22 to permit regulation of the relative quantities of metal applied to the two chambers. Pump 1'7 is driven by motor 19 through suitable gears (not shown) so which are enclosed in gear box 18. Bracket so may be secured to the assembly in a position to receive. a lifting device and permit the entire assembly to be removed from the kettle. Rim 31 may also be secured to framework it for strength as ening purposesand to provide aguard rail for the operator; g

Suitable inlet pipes 32 and 33 are associated with chambers 15 and it and are provided with valves 34 and 35 respectively. These pipes serve 96 to admit the reagent in controllable quantities to the reaction chambers wherein it contacts with the molten metal from pipes 23 and 24. Said chambers are also provided with discharge pipes 36 and 37 respectively which extend from the bot tom of the chambers into the bath of metal and are preferably inclined toward each other whereby mixing of the products of reaction from the two chambers is obtained.

A separate stirring device comprising an im- 1% peller 4c and suitable driving means is mounted on a separate framework comprising longitudinal means 41 which are also supported across the rim of the kettle. Said framework carries driving motor 42 and gear box 43 containing a suitable reduction gear by which the impeller is rotated. Shafts id and 45 connect the gears with the driving motor and impeller respectively. The impeller is designed so that upon rotation thereof at a predetermined speeds, vortex is produced in the 11m metal bath by means of which the material resting upon the surface of said bath is drawn below said surface and a thorough mixing of the various portions of the bath is obtained.

The process as applied to the dezincing of lead may be carried out by pumping lead from the Parkes desilverization process into kettle 10 at a temperature of 750 to 800 F. Zinc oxychloride slag from a preceding operation may then be added to the dezincing kettle together with a small percentage (by weight) of commercial sodium borate, borax and/ or sodium chloride. The latter materials operate as fluxes and serve to increase the fluidity of the slag whereby the reactions are more efiiciently carried out.

The bath and slag-are then mixed by starting the mixing apparatus including impeller 40 which is operated to produce a good vortex. This mixing may be carried out, for example, for some 30 minutes and serves to bring the oxychloride slag into intimate contact with the bath whereby a considerable portion of the lead held mechanically is removed and also the lead resulting from the reduction of oxidized lead in the slag by reaction with the zinc present in the said bath and both are thus removed from the slag by entering the said metal bath. The slag may then be removed from the surface of the bath as by skimming or trapping and treated for further deleading in a manner to be hereinafter described.

After the slag has been removed the dezincing apparatus is then applied to the bath and a supply of reagent, such as chlorine gas, is connected to one of the inlet pipes, for example, pipe 32 and the other of said pipes 33 is connected to a source of oxidizing agent, such as compressed air.

Pump 17 is then started and brought up to operating speed, after which valves 25, 26 and 27 are opened and the molten lead supplied to the two chambers 15 and 16. Valve 25 is preferably kept closed until the pump has been brought up to operating speed so that molten metal is not applied through the pipes or to the reaction chambers until sufficient quantities thereof can be circulated to prevent the apparatus from freezing. Thereafter, the relative supply of the metal to the two chambers is controlled by suitable regulation of valves 26 and 2'7.

After the circulation has been established, the oxidizing agent, such as compressed air, is admitted to chamber 16 by suitable regulation of valve 35 and serves to react with the metal flowing through the chamber and to preferentially combine with the zinc to form zinc oxide. While the reaction with the zinc is exothermic, the rapidity of the reaction is not sufiicient under the above conditions to generate suflicient heat to balance the heat lost from the reaction chamber and from the metal bath. The process is accordingly carried on as above described until the temperature of the bath decreases to approximately 750 F. Thereafter, chlorine gas is admitted to chamber 15 by suitable regulation of valve 34. to react with the metal passing therethrough and form zinc chloride and to produce suflicient heat to maintain the temperature of the bath substantially constant. By balancing the amount of reaction taking place in the two chambers, as by means of valves 26 and 2'7 and valves 34 and 35, it is possible to conserve the heat which is produced so as to maintain the temperature of the bath substantially constant with the use of a minimum amount of fuel.

During the above reaction a quantity of zinc chloride slag resulting from the removal of the final zinc from previous operations is added to the bath and serves as an additional flux to first remove the oxidized coatings from the metallic portions of the dross, thus allowing them to coalesce and settle back into the bath and second to render the resulting oxychloride slag fluid at the temperatures employed in the process. At convenient intervals the mixing machine is. also operated to cause an intimate mixture of the zinc oxide and zinc chloride which is obtained from the two chambers whereby a zinc oxychloride slag is produced. Borax and/or sodium chloride may also be added at this stage of the operation to increase the fluidity of the slag and to produce a fluid, uniform oxychloride slag of zinc which contains some lead.

The operation above described may be continued until the zinc content of the bath is reduced to comparatively low limits, as, for example, .10% to .15%. It is usually undesirable to carry the reaction below this point inasmuch as the selective oxidation of zinc depends upon the relative quantities of zinc and lead and the slag would become unduly contaminated with lead oxide if the reaction were further continued. Accordingly, the operation is stopped and the oxychloride slag, which contains some lead oxide in solution, is removed as by skimming or tapping and is applied to subsequent baths for deleading, as above described.

After removing the oxychloride slag, circulation of the metal is continued through reaction chamber 15 and the application of chlorine thereto is continued until the zinc is removed from the lead to the desired low percentage. The zinc chloride slag containing small amounts of lead chloride which results from this operation is then skimmed from the kettle and used as a flux in the dezincing of further quantities of lead bullion in accordance with the above process. The remaining lead is substantially free from zinc and is suitable for commercial use.

The final deleading of the zinc oxychloride slag referred to above may be accomplished by melting the same over a bath of metallic zinc or a lead zinc alloy in the presence of sufiicient sodium chloride and/or borax to cause the slag to remain fluid at the temperature involved. The operation is preferably carried out by melting the slag and zinc or lead zinc alloy in a suitable kettle, placing the suitable mixing device therein under a heat insulating coverand mixing at a temperature of approximately 850 F. The borax may, if desired, be added to the vortex produced by the mixing machine and the mixing continued until a complete reaction between the "slag and the zinc of the bath has been obtained. Thereafter, the bath is allowed to settle and the slag may be skimmed or tapped therefrom substantially free from zinc or metallic zinc bath the lead in the oxychloride slag will be reduced to percentages of .8% to 1.9%.

The oxychloride slags are sensitive to slight changes in temperature and are easily chilled lead. By the use of the lead with resultant loss of fluidity. For this reason the temperatures in the deleading kettle must be accurately controlled and the heat insulating cover is of particular importance. Temperatures in excess of 900 F. are objectionable due to the formation of a zinc iron alloy, the iron being derived from the kettle.

In accordance with the present process the necessity for such high temperatures is avoided 'by the use of a suitable amount of flux which ber. 11, 1931, for

turning the products of reaction and unreacted increases the fluidity of the slag at the temperatures above specified. The fluidity is of considerable importance inasmuch as the lead present in the slag, as a result of reduction by the Zinc 01' the bath employed, is in the nature of prills which must be allowed to coalesce and settle out of the final slag. I

The cover for the deleading kettle may be handled by a suitable overhead crane. In suitable position the circulating pump is in the bath of molten slag below the cover with the motor in the outside atmosphere above the cover.

The total additions of borax comprises approximately 2 leaded oxychloride. slag and the sodium chloride additions may amount to 5% to 10% thereof.

By the above process oxychloride slags may be produced which vary in chlorine content from normal zinc chloride up to oxychloride slags containing of the zinc as ZnO and 25% as ZnClz. It is obvious that chlorine gas will only be required in chemical equivalent amounts to the ZnClz existing in the final slag.

The process is made possible by reason of the fact that zinc is preferentially oxidized by either air, steam or water at low temperatures in the range of 630 F. to 750 F. Obviously, the reagents may be introduced intothe bath in various ways, such, for example, as through the reaction cylinder of the dezincing machine or through outlets located under the blades of the mixing machine, or in any other manner, thus allowing a thorough dissemination of these reagents through the molten bath.

A dry dross is produced, but due to the low temperatures most of the lead in the dross is present as metallic particles and all of the zinc as fine powdered zinc oxide. This condition permits the process to be treated with a flux, such as the zinc chloride slag above mentioned, which is capable of removing the oxidized coatings from the surfaces of the lead prills and allowing them to coalesce-and settle. out of the slag.

This application is a division of the co-pending application of Jesse O. Betterton and Yurii E. Lebedeif, Serial Number 574,328, filed Novem- Apparatus for treating metals.

While certain novel features of the invention have been disclosed and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. The process of treating lead to remove an oxidizable and chloridizable constituent therefrom which comprises forming a bath of said lead, continuously withdrawing portions of said lead, from said bath, dividing the portions so withdrawn into a plurality of parts and separately treating said parts with a chloridizing agent and'oxidizing agent respectively whereby said constituent is removed from said parts as a chloride and oxide respectively, returning the unreacted lead and the products of reaction to said bath and causing said oxide and chloride to be combined to form an oxychloride slag, allowing said slag to rise to the surface of said bath and removing the same from contact with said bath.

2. The method of treating molten lead to'remove chloridizable and oxidizable contaminants therefrom which'comprises subjecting separate portions of such lead to the action of a chloridizing agent and an oxidizing agent respectively. re-

of the weight of the flnal demetal of said portions to the source of metal, effecting the formation of an oxychloride slag from the products of reaction and separating said slag from the purified metal.

3. The process according to claim 2 in which the molten metal-is covered with a low melting cover slag.

4. The process of dezincing lead which comprises forming a bath of molten lead, removing portions of said bath and separately applying chlorine and an oxidizing agent to the respective portionsto form zinc chloride and zinc oxide, returning the unreacted molten lead and the products of reaction to said bath and causing said chloride and oxide to mix to form an oxychloride slag which rises to the surface of the bath and may be removed therefrom.

5. The process of dezincing lead which comprises forming a bath of molten lead, removing portions of said molten lead from said bath and separately applying chlorine and an oxidizing agent thereto whereby zinc chloride and zinc oxide are formed, controlling the relative quantities of zinc chloride and zinc oxide thus obtained, returning the unreacted metal and the products of reaction to said bath and mixing said products of reaction whereby an oxychloride slag is formed having predetermined amounts of oxygen therein, which slag floats upon the surface of the bath and may be removed therefrom.

6. The process of dezincinglead which comprises forming a bath of said lead, removing portions of said bath and circulating the same through reaction chambers containing an oxidizing agent and chlorine respectively whereby zinc oxide and zinc chloride are formed therein, controlling the relative quantities of metal applied to said chambers whereby a heat balance is obtained and the temperature of the bath is maintained substantially constant, returning the unreacted lead and the products of reaction to said bath wherein they become mixed to produce an oxychloride slag, adding a zinc chloride slag to said bath to serve as an additional flux for the removal of the oxidized coatings from the metallic portions of the dross and thus allowing them to coalesce and settle out of the slag into the bath, this fluxing action also resulting in the production of a liquid slagwhich floats on the surface of the bath and may be removed therefrom.

'7. The process of dezincing lead which comprises forming a bath of said lead, removing portions of said bath and circulating the same through reaction chambers containing an oxidizing agent and chlorine respectively whereby zinc oxide and zinc chloride are formed therein, controlling the relative quantities of metal applied to said chambers whereby a heat balance is obtained and the temperature of the'bath is maintained substantially constant, returning the unreacted lead and the products of reaction to said bath wherein they become mixed to produce an oxychloride slag, adding a zinc chloride slag to said bath to serve as an additional flux for the removal of the oxidized coatings from the metallic portions in the dross thus allowing them to coalesce and settle out of the slag into the bath, this fluxing action also resulting in a production of a liqud 'slag which floats on the surface of the bath, adding a flux to said slag to increase the fluidity thereof whereby an oxychloride slag of still greater fluidity is formed and removing said slag from contact with said bath. I

8. The process of dezincing lead which comprises forming a bath of said lead, removing portions of said bath and circulating the same through reaction chambers containing an oxidizing agent and chlorine respectively whereby zinc oxide and zinc chloride are formed therein, controlling the relative quantities of metal applied to said'chambers whereby a heat balance is obtained and the temperature of the bath is maintained substantiallly constant, returning the vun'reacted lead and the products of reaction to saidbath wherein they become mixed to produce an oxychloride slag, adding a zinc chloride slag to said bath to serve as an additional flux for the removal of the oxidized coatings from the metallic portions in the the dross thus allowing them to coalesce and settle out of the slag into the said bath, this'fluxing action also resulting in a production of a liquid slag which floats on the surface of the bath, adding borax an'd/or sodium chloride to said slag to increase the flu-' idity thereof whereby an oxychloride slag of still greater fluidity is formed and removing said slag from contact with said bath.

9. The process of dezincing lead which comprises forming a bath of said lead, removing portlons thereof irom said bath and treating said portions with chlorine and an oxidizing agent, returning said portions together with the products of reaction to said bath whereby said products are mixed to form an oxychloride slag, continuing the treatment until the zinc content of the bath is at .10% to 15%, then removing the oxychloride slag and continuing the treatment with chlorine only whereby zinc chloride is produced until the zinc content of the bath is reduced to the desired low value.

10. The process of dezincing lead which comprises forming a bath of said lead, removing portons thereof from said bath and treating said portions with chlorine and an oxidizing agent, returning said portions together with the products of reaction to said bath whereby said products are mixed to form an oxychloride slag, continuing the treatment until the zinc content of the bath is at .10% to 15%, then removing the oxychloride slagand continuing the treatment with chlorine only whereby zinc chloride is produced until the zinc content of the bath is reduced to the desired low value, removing the zinc chloride asa slag and returning the same to subsequent baths-in the step of forming an oxychloride slag, sad zinc chloride serving as a flux to tallic portions first remove .the oxidized coatings from the meand thus allowing them to coalesce and settle out of the slag into the said bath and second to render the resulting oxychloride slag, thus freed from metallics, fluid at temperatures employed in the process.

11. The process of dezincing lead and removing the zinc in commerc'ally usable form which comprises forming a bath of said lead, treating said bath with chlorine and an oxidizing agent under conditions whereby a zinc oxychloride slag is formed, removing said slag, return'ng the same to subsequent baths of lead prior to the dezincing operation whereby said slag is partially deleaded, removing said partially deleaded slag and melting the same over a bath of zinc and/or a' lead zinc alloy in the presence of borax and sodium chlo ride whereby finaldeleading is accomplished and the zinc oxychloride in commercially usable form is obtained.

12. The process of dezincing lead and removing the zinc in commercially usable form which comprises forming a bath of said lead, treating sai bath with chlorine and an oxidizing agent under conditions whereby a zinc oxychloride slag is formed, removing said slag, returning the same to subsequent baths of lead prior to the dezincing operation whereby said slag is partially deleaded, removing said partially deleaded slag and melting the same over a bath of zinc and/or a lead zinc alloy at a temperature of 800 F. to 850 F. whereby final deleading is accomplished and zinc oxychloride in commercially usable form is-obtained.

13. The process of dezincing lead which comprises forming a bath of molten lead, treating said bath with chlorine and an oxidizing agent to form a zinc oxychloride slag, removing said slag and returning the same to subsequent baths of lead prior to the dezincing treatment whereby said slag is partially deleaded, removing said partially deleaded slag and melting thesame over a bath of zinc and/ or a lead-zinc alloy to further delead said slag and removing from said bath said slag from which the lead has been reduced to a percentage conforming to commercial requirements.

14. The process of deleading a zinc oxychloride slag which comprises melting said slag over a bath of zinc and/ or a lead zinc alloy at a temperature of 800 to 850 F. in a heat insulated kettle whereby a uniform temperature is obtained throughout the bath, said treatment taking place in the presence of borax and/or sodium chloride whereby the fluidity of the slag at the above temperatures is increased.

15. The process of dezincing lead and removing the zinc in commercially usable form which comprises forming a bath'of said lead, treating said bath with chlorine and an oxidizing agent under conditions whereby a zinc oxychloride slag is formed, removing said slag, returning the same to subsequent baths of lead prior to the dezincing operation whereby sad slag is partially deleaded, removing said partially deleaded slag and melting the same over a bath of zinc and/or a lead zinc alloy in the presence of a flux capable of increasing the fluidity thereof whereby final deleading is accomplished and the zinc oxychloride in commerc'ally usable form is obtained.

16. The process of dezincing lead which comprises melting said lead at a temperature of 150 F. to 800 F., adding a zinc oxychloride slag thereto in the presence of sodium borate and borax and/ or sodium chloride, thoroughly incorporating said materials in said bath by stirring said bath to produce a vortex therein whereby said zinc oxychloride is partially deleaded, skimming said deleaded slag, treating the same for removing further quantities of lead and producing a commercially usable zinc oxychloride, treating the lead bath for the removal of zinc therefrom by applying chlorine and an oxidizing agent thereto to form a zinc oxychloride slag, adding zinc chloride, borax and/or sodium chloride to said bath to increase the fluidity of saidslag, removing said slag when the zinc content has been reduced to 10% to 15% and applying said slag to subsequent baths for deleading in the steps above mentioned, thereafter applying chlorine to the lead bath to form zinc chloride until the zinc content of the bath has been reduced to the desired value, removing the zinc chloride and applying the same to subsequent baths in the step above mentioned whereby said chloride is utilized as a flux and the lead is recovered therefrom.

JESSE O. BETTERTON. YURII E. LEBEDEFF. 

